Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include <bits/stdc++.h>

using namespace std;

typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PI;

int dx[4] = { 1, 0, -1, 0 }, dy[4] = { 0, 1, 0, -1 };

int main() {
	int h, w;
	cin >> h >> w;
	char s[50][50];
	int dist[50][50] = {};
	int cnt = 0;
	for (int j = 0; j < h; j++)
		for (int i = 0; i < w; i++) {
			cin >> s[i][j];
			if (s[i][j] == '.')
				cnt++;
			dist[i][j] = 100;
		}
	queue<PI> q;
	q.push({ 0, 0 });
	dist[0][0] = 1;
	while (!q.empty()) {
		PI t = q.front(); q.pop();
		for (int i = 0; i < 4; i++) {
			int ny = t.first + dy[i];
			int nx = t.second + dx[i];
			if (ny < w && ny >= 0 && nx < h && nx >= 0) {
				if (s[ny][nx] == '.')
					if (dist[t.first][t.second] + 1 < dist[ny][nx]) {
						dist[ny][nx] = dist[t.first][t.second] + 1;
						q.push({ ny, nx });
					}
			}
		}
	}
	if (dist[w - 1][h - 1] == 100)
		cout << -1 << endl;
	else
		cout << cnt - dist[w - 1][h - 1] << endl;
	return 0;
}